Consolidated Statements of Equity - USD ($) $ in Thousands	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	Treasury Stock [Member]	Noncontrolling Interest [Member]	Total
Balance (in shares) at Apr. 30, 2014	12,452,809
Balance at Apr. 30, 2014	$ 125	$ 55,734	$ 264,348	$ (107,301)	$ 100	$ 213,006
Issuance of common stock (in shares)	3,831
Issuance of common stock		146				$ 146
Stock options exercised (in shares)	212,250					212,250
Stock options exercised	$ 2	4,141				$ 4,143
Purchase of treasury shares				(20,020)		(20,020)
Tax benefit of stock based compensation		1,627				1,627
Stock based compensation (in shares)	20,000
Stock based compensation		780				780
Dividends on subsidiary preferred stock			(40)			(40)
Net income			29,490			29,490
Balance (in shares) at Apr. 30, 2015	12,688,890
Balance at Apr. 30, 2015	$ 127	62,428	293,798	(127,321)	100	229,132
Issuance of common stock (in shares)	6,920
Issuance of common stock		186				$ 186
Stock options exercised (in shares)	30,750					30,750
Stock options exercised		400				$ 400
Purchase of treasury shares				(14,214)		(14,214)
Tax benefit of stock based compensation		238				238
Stock based compensation		1,519				1,519
Dividends on subsidiary preferred stock			(40)			(40)
Net income			11,596			11,596
Balance (in shares) at Apr. 30, 2016	12,726,560
Balance at Apr. 30, 2016	$ 127	64,771	305,354	(141,535)	100	228,817
Issuance of common stock (in shares)	4,750
Issuance of common stock		142				$ 142
Stock options exercised (in shares)	196,103					264,500
Stock options exercised	$ 2	1,895				$ 1,897
Purchase of treasury shares				(20,489)		(20,489)
Tax benefit of stock based compensation		1,183				1,183
Stock based compensation		1,293				1,293
Dividends on subsidiary preferred stock			(40)			(40)
Net income			20,205			20,205
Balance (in shares) at Apr. 30, 2017	12,927,413
Balance at Apr. 30, 2017	$ 129	$ 69,284	$ 325,519	$ (162,024)	$ 100	$ 233,008